Who killed Napoleon? How did he die? Who is in his tomb?Napoleon Bonaparte is said to have died on St Helena in 1821. We now know, beyond reasonable doubt, how he was killed and who did it. But several experts agree that the bones in the emperor's tomb are those of an impostor. Richard Girling investigates

So why, last summer, did a French lawyer, Bruno Roy-Henry, apply to the French defence ministry for the corpse to be dug up again and DNA-tested ? And why did the ministry refuse ? The answer to both questions may be the same. Roy-Henry is one of a growing number of critics who have been arguing for 30 years that the bones in Les Invalides are those of an impostor.

His argument, set out in his book Napoléon, L'Enigme de l'Exhumé de 1840, relies on discrepancies in the accounts of the burial in 1821, and the exhumation in 1840. In 1821 the ribbon of Napoleon's Légion d'Honneur was arranged on top of his uniform coat. A cockaded hat rested on his feet. He wore silk stockings and riding boots with silver spurs, and the silver urns containing his heart and stomach were placed in the corners of the coffin. His face and head were smoothly shaven and his mouth was closed, but the unembalmed body was so badly putrefied that his face was unrecognisable.

In 1840 the Légion d'Honneur was under his clothing, and the coat itself was a different one. The hat had lost its cockade and moved to his thighs; the stockings and spurs had vanished, the stitching of the boots had been undone to expose his toes, and the urns had moved up between his legs. The corpse was now bearded and had hair on its head. Its mouth was open and the face was young-looking, without disfigurement. The body had been embalmed.

Roy-Henry's suspicions fall upon the ancient enemy. The perfidious English, he suggests, stole away the emperor's remains and hid them in Westminster Abbey. In his place they left the corpse of his major-domo, Franceschi Cipriani, a fellow Corsican of strikingly similar appearance (but larger feet - hence the unstitching of the boots). To the real revisionists, however, none of this is worth a row of haricots verts. So what if the English robbed the grave? The joke is on them. The body they stole was no more Napoleon's than the one they left in its place. True, a middle-aged man of small stature and hooked pharaonic nose dies and is buried on St Helena in May 1821, just as the history books record.But he is not Napoleon Bonaparte. There is nothing new in the idea that Napoleon employed doubles. Dame Mabel Brookes, a historian whose family lived on St Helena at the time of Napoleon's exile and knew him well, was certain of it. In her influential book St Helena Story, published in 1960 and heavily reliant on family memoirs, she insists that there were four of them. 'One might imagine,' says Dr Alexander Gorbovsky, 'that the emperor fearlessly galloping in front of his troops under enemy fire was not always the man he seemed.' By Brookes's account, impersonating a military genius was no soft option. One of the doubles was killed by a bullet. Another was poisoned before Waterloo. Another was thrown from his horse and crippled. And the fourth... Well, we shall see what happened to the fourth.

Alexander Gorbovsky is a 72-year-old Russian historian, now based in London, who worked for 20 years in the USSR's Academy of Sciences. While in England he has been sifting through the Napoleonic literature - a literature so vast that no historian on earth can possibly have read all of it. Worldwide, the number of books on Napoleon exceeds 200,000. As so many have done before him, Gorbovsky immediately caught the whiff of foul air that surrounds the emperor's death. On May 3, 1821, a courtier writes: 'At 11.30 the emperor had a bowel movement. It was black, enormous, larger alone than all those he had for a month.' But the servants do not understand the significance of what they have seen. They heave up Napoleon's dead weight and change the sheets.

What fascinates Gorbovsky is the story of Fran�ois Eug�ne Robeaud, a rabbit breeder of Baleycourt in the Meuse, who is the only one of Napoleon's doppelgangers whose name survives. In the village register, his death is recorded thus: 'Born in this village, died on St Helena...' The date has been obliterated.

After Napoleon's defeat, says Gorbovsky, Robeaud's career as imperial body-double was terminated. He returned to Baleycourt, where he lived with his unmarried sister. The seasons passed and he slipped back into the easy rhythms of rural life, a forgotten soldier of the revolution. Forgotten, that is, until the summer of 1818, when there arrives in Baleycourt a carriage of such opulence that nobody will forget it. The passengers remain hidden behind curtains, and it is left to the coachman to ask the way. He is looking, he says, for the house of Francois Eugene Robeaud. Even today, such a visitation to a small rural community would not pass without notice. In 1818 it is sensational. Pressed by his neighbours, Robeaud claims his mysterious visitor was a travelling doctor who wanted to buy rabbits for a friend. And there it might have rested, had it not been for what happens next.

Robeaud and his sister disappear. They go at night, without telling anyone and without saying goodbye - behaviour that causes frank astonishment. A year later, police find Robeaud's sister living comfortably in Nantes. Why they went to such trouble over a humble farmer and his sister is in itself a cause of wonder. The woman's story is that she is being maintained, for reasons of altruism, by the very same doctor who came to buy rabbits. She offers no explanation for their flight, and can say of Francois only that he is 'a sailor at sea, on a long voyage'.

Late in the same year, a tall blonde woman begins a letter to a friend in France. 'Success is ours!' she writes. 'Napoleon has left the island.' The writer is Fanny Dillon Bertrand, part-Irish wife of Count Henri-Gratien Bertrand, a senior member of Napoleon's household in exile.

Rumours fly. A fast American ship has been seen hanging about on the horizon. Napoleon himself has become increasingly reclusive, refusing to show himself to English officers. Visitors who do see him report puzzling changes in his behaviour. The Russian representative on St Helena, Count Balmain, is surprised by a sudden interest in farming. 'Now Napoleon has a fantasy to become a shepherd. He buys all the pretty lambs of the island and amuses himself feeding them under his windows.'

More shockingly, he records a visit to Napoleon by a relative of the English prime minister Lord Liverpool: 'Bonaparte received him in a room which was completely dark. After a quarter of an hour's conversation he ordered candles to be brought in and said, 'I want to see you'. He was abed in a flannel dressing-gown and had a red turban on his head. His face was unshaven for several days.' To the courtly Balmain, this was a gross and inexplicable breach of etiquette: 'At least he could put on his trousers.'

Gorbovsky is not the only one to have weighed the evidence - Napoleon's reclusiveness, his change of behaviour, the hovering American ship, Fanny Bertrand's letter - and concluded that the emperor had flown the coop and been replaced by a rustic from the Meuse. Napoleon's family at the time are in no doubt. His mother, Laetitia, known as 'Madame Mere', and his uncle Cardinal Joseph Fesch are unconcerned by reports of the prisoner's declining health, for they are sure he is not their boy. In a letter, Fesch insists: 'Although we know neither the place where he presently resides nor the time when he will reveal himself, we have valid proofs of our assertion.' The valid proofs, however, may not be of the kind that would satisfy a jury. According to Napoleon's sister Pauline, Madame Mere and the cardinal were in thrall to a German clairvoyant who received the news directly from the Virgin Mary: 'His Majesty has been taken away by angels and transported to another country where his health is very good.'The health of the man left in St Helena, however, is not good at all. In all, eight of his companions on the island are keeping journals or making notes. Four of them (three English, one Italian) are doctors. The others are members of his entourage, including his observant and ultra-loyal valet Louis Marchand. Between them they record more than 30 symptoms of an illness to which none of them can put a name. The catalogue of suffering includes swollen feet, loss of body hair, uncontrollable weight gain, nausea, headache, dizziness, irregular pulse, pain in the liver and stomach, constipation, diarrhoea, loose teeth, bleeding gums, weakness in the legs, deafness, impaired vision, unquenchable thirst, drowsiness and insomnia. Some days are better than others, but the patient is obviously deteriorating. By early 1821 it is clear that a crisis is imminent.

On February 26, the Italian doctor Francesco Antommarchi reports: 'The Emperor, who was feeling fairly well on the 21st, has a sudden relapse. Dry cough. Vomiting. Sensation of heat in intestines. Generally disturbed. Discomfort. Burning feeling that is almost unbearable, accompanied by burning thirst.' Next day: 'The Emperor is worse yet than yesterday. The cough has become more violent, and the painful nausea did not stop until seven in the morning.'

As a last resort the doctors prescribe emetics in the hope that the emperor - by now grossly fat - will expel his illness by vomiting. Finally, at 5.30pm on May 3, he is given a massive dose of calomel, a brutish laxative. 'Shortly afterwards,' notes Henri-Gratien Bertrand, 'he fell unconscious. He was completely immobilised by a total paralysis of the voluntary muscles. He could not even swallow.' The end comes two days later. Following an autopsy on May 6, the doctors conclude that death was due to 'a condition leading to cancer'.

This was not the only death on St Helena in the early months of 1821. In late February, Napoleon's robustly healthy major-domo (and probable secret agent), Franceschi Cipriani - the man whose body Bruno Roy-Henri believes now lies in Les Invalides - is hastily buried after being struck down by suspiciously sudden stomach pains and violent chills. When a postmortem is proposed, the grave is found to be empty.

Dame Mabel Brookes's great-grandfather William Balcombe, a merchant with the East India Company, was Napoleon's host on St Helena before Longwood House was ready for him. He and his family provide important insights for historians, and it is Mabel Brookes herself, in St Helena Story, who alerts Dr Gorbovsky to the next twist in the tale. In 1818, shortly after Fanny Bertrand writes her letter, a ship drops anchor at Verona and discharges a passenger. The new arrival, a middle-aged man of short stature with a pharaonic nose, speaks perfect Italian and introduces himself as Signor Revard. He is a gentleman of independent means who quickly finds himself a business partner, a diamond trader called Petrucci. Such is the newcomer's appearance that the townspeople call him by the obvious nickname, 'Napoleon' - a joke that draws from Revard only the thinnest of smiles. Strangely for a man of wealth, he is an appalling businessman whose every transaction results in loss. Stranger still, according to Petrucci, he doesn't seem to care. 'Evidently,' says Gorbovsky, 'profit and money were matters of indifference.'

We move on to the hour of noon on August 23, 1823 (Petrucci is very precise about the time). A messenger arrives and hands to Revard a sealed letter. Reading this, Revard shows untypical signs of anxiety and speaks of 'urgent business' elsewhere. Two hours later he reappears in travelling clothes and gives Petrucci an envelope. If he does not return within three months, he says, Petrucci personally must deliver it to an address in Paris. As the clatter of Revard's carriage dies in the distance, Petrucci reads what is printed on the envelope: 'To His Highness the King of France'.

Twelve days later, Napoleon's 12-year-old son, Fran�ois Charles Joseph, nicknamed l'Aiglon (the eaglet), is very ill with scarlet fever in Schšnbrunn Castle, Vienna, where he is held with his mother, Marie-Louise. On the night of September 4, an intruder is caught descending the castle wall and is shot by a guard. There is a commotion when officers bring a light, and the corpse is locked in a shed while a message is taken to the French embassy. The embassy later tries to claim the body but is thwarted by Marie-Louise, who has it buried in an unmarked grave at Schšnbrunn.

'Revard' is never seen again. Petrucci duly delivers the letter to Paris, receives a reward of 100,000 crowns and keeps his silence for 30 years. Only then, in a sworn statement before the authorities in Verona, does he relate his story. His one-time partner, he says, was no joke 'Napoleon'. He was Bonaparte himself. One of Napoleon's most singular features was his hair. He grew it long and was in the habit of giving locks of it to visitors and servants, many of whom recorded the gifts in their memoirs and passed them on as heirlooms. Recipients included the portrait painter Jean B Isabey, who received a lock of it in April 1805; two English naval officers, Cmdr John Theed of HMS Leveret on January 14, 1816, and Admiral Sir Pulteney Malcolm on July 3,1817; the teenage Betsy Balcombe - daughter of William Balcombe and great-aunt of Dame Mabel Brookes - who received two locks before her family's departure from St Helena in March 1818; and the valet Louis Marchand, who kept hairs shaved from the head of the corpse.

All these samples still survive, and might have remained little more than historical curios if not for two men: the late Dr Sten Forshufvud, a Swedish biologist and toxicologist; and Ben Weider, president of the Montreal-based International Napoleonic Society, whose books have promoted Forshufvud's theories. Put simply, in 1955 Forshufvud read Louis Marchand's account of the last days on St Helena - an account that Marchand himself never intended for publication and that did not appear in print until that same year, 1955. Forshufvud saw immediately that the medical diagnosis made no sense. Officially, the prisoner on St Helena had died of 'a condition leading to cancer'; yet in Marchand's meticulous journals Forshufvud could find no mention of any symptom of cancer. More puzzling still, the sick man had been piling on weight. One seldom hears of fat cancer victims. The more Forshufvud read, the more he saw that the evidence - the multiplicity of apparently unrelated symptoms, the good and bad days, the swollen liver noted at the autopsy - all pointed to the same conclusion. Napoleon had been the victim of the classic murder weapon of his day - arsenic.

Painstakingly, over many years, Forshufvud tracked down locks of Napoleon's hair in France, Switzerland, England, Russia and Austria, and begged each owner for a sample. One by one - 140 samples in all - these were sent for analysis by a leading British forensic scientist, Professor Hamilton Smith, at the University of Glasgow, and subsequently to the Atomic Energy Research Establishment at Harwell. The tests proved two things. All the samples were from the same person. And their owner had ingested regular doses of arsenic. Even the earliest sample, from 1805, showed a level of arsenic 20 times higher than normal. Evidently, Napoleon by then was already the subject of a murder attempt - unsurprisingly perhaps, given the hatred of Europe's royal families, especially the French Bourbons, and their anxiety to see him dead. The St Helena samples seemed to put the issue beyond doubt. Crucially, the tests do not give a single overall reading but grade the hair in sections. Providing you know when the sample was taken, you can work back along its length and calculate almost to the day when arsenic entered the body. The hair at death was 3in long and gave a continuous record of the last six months of life. Concentrations of arsenic ranged between 2.8 and 51.2 parts per million (this at a time when the human average was 0.08). All Forshufvud and Weider had to do was make a time chart of the symptoms listed by Marchand and the doctors, and compare it with the arsenic record from the hair. They matched precisely.

In the end, however, it was not the arsenic itself that killed. Ironically, what finished Napoleon off was the medication given to soothe its effects. In March 1821 he was given 'tartar emetic' in lemonade to make him vomit. Chemists know this as antimony potassium tartrate. It is highly toxic and has the effect of corroding the mucous lining of the stomach - thus inhibiting the very vomiting reflex it is meant to stimulate, and robbing the stomach of its ability to expel poisons.

Two more things hit Napoleon's system at about the same time: an orange-flavoured drink called orgeat, and calomel laxative. Orgeat contains oil of bitter almonds, a source of prussic acid, more ominously known as hydrocyanic acid or hydrogen cyanide. Calomel contains mercury chloride. In the body these combine to form mercury cyanide, a poison that an undamaged stomach might have been expected to reject. If not expelled, it further corrodes the stomach walls and causes muscular paralysis - symptoms precisely reflected in the manner of death and condition of the dead man's stomach. It also explains the appalling black bowel movement recorded on May 3 - the blackness caused by blood from the stomach and the inky colour of metallic mercury.

Cause of death according to Forshufvud and Weider: 'cyanide poisoning following chronic arsenic intoxication'. Which is exactly how poisoners of the time went about their business. Whoever murdered Napoleon would not have wanted to kill him outright, for this would have risked a revolutionary backlash in France. Much better to poison him slowly, gradually breaking down his health and making his deterioration look like chronic disease. At the end, physicians would oblige the murderer with unsurvivable doses of common emetics and laxatives.Who, then, was the guilty man? As poisoning occurred throughout the whole of Napoleon's exile, the poisoner must have been there the whole time too. He must have been in close contact with his victim and must have had access to his food or drink. Only two men fit the bill: the valet Louis Marchand and the playboy courtier Count Charles Tristan de Montholon.

The discretion and loyalty of Marchand, and the absence of motive, reduce this to one. Unless Montholon is the murderer, his presence on St Helena is all but inexplicable. He has a grudge against Napoleon, who dismissed him from his position as envoy to WŸrzburg for making an unsuitable marriage; and he was a staunch royalist whose family linked him to both Louis XVIII and his brother, the Duke d'Artois, later Charles X. D'Artois in particular was an inveterate plotter whose dearest wish was Napoleon's death. It was Louis who appointed the loose-living, unscrupulous Montholon to the rank of general while Napoleon was exiled on Elba; and d'Artois who saved Montholon from punishment when he embezzled army funds in 1814. Thus might d'Artois have secured a hold over Montholon and sent him to St Helena.

Why else would a fast-living metropolitan rake volunteer to be marooned in mid-Atlantic? Why else would he remain there, uncomplaining, in the almost certain knowledge that his wife, Albine - ironically in the light of Napoleon's earlier objection to her - was sharing the emperor's bed?

How did he do it? Napoleon enjoyed a private supply of wine - vin de Constance from Cape Town - which he kept to himself. For a man of Montholon's intelligence, it would have been a simple matter to open a bottle and add the measured dose. As arsenic lacks odour and taste, Napoleon would have had no reason to connect his wine with the loss of body hair, bulging waistline, malfunctioning limbs and howling stomach. In the absence of modern forensics, the murder of Napoleon Bonaparte would have been the perfect crime. Assuming, of course, that Napoleon Bonaparte was the man who died. Historical orthodoxy is not easily blown off course. Revisionists have a hard time of it making their voices heard above the gales of outrage and joining waters of academic conservatism. Once in a while, however, comes a piece of evidence that even the die-hards find hard to dismiss. Forshufvud and Weider's arsenic record is a brilliant example. Britain's leading Napoleonic historian, Dr David Chandler, former head of the department of war studies at Sandhurst, and author of standard works such as The Military Maxims of Napoleon and On the Napoleonic Wars, is unequivocal.

'That Napoleon died of poison is now clear,' he says. 'I accept that now, though for years I was uncertain.'

He has also researched the character and behaviour of Montholon and, though he agrees the evidence is circumstantial, is convinced that Forshufvud and Weider have fingered the right man.Crime investigators agree. In 1995 the US Department of Justice declared that the analysis of the hair was 'consistent with arsenic poisoning', and in 1997 Scotland Yard said the same. In June 2001, Ben Weider delivered what most neutral observers now accept was the clincher. For years, French historians had refused to accept the evidence of tests conducted outside France. Now Weider was able to reveal that five samples of hair had been examined by Dr Pascal Kintz in the department of toxicology at the University of Louis Pasteur in Strasbourg. Kintz's conclusion: 'There was major exposure, and I stress major, to arsenic.'

On October 2 this year, a direct descendant of the Count de Montholon, Francois de Cande-Montholon, wrote to Weider fully accepting his ancestor's guilt.

Further than this, however, most professional historians are reluctant to go. David Chandler is unconvinced by Roy-Henri's body-snatching theory, but adds a teasing footnote to the persistent rumour that the urn holding Napoleon's stomach somehow found its way to England. 'About 25 years ago,' he says, 'I was told by a senior general of the Royal Army Medical Corps that it was destroyed by German bombing in 1941.'

Weider is frankly scornful. 'The reason why it is impossible to believe that Napoleon's body is not at Les Invalides is the very fact that several of his companions, who shared the entire exile with him and who witnessed placing the body in the tomb, were present when it was removed from St Helena to be sent back to Paris.'

Petrucci's story similarly fails to impress. 'It's linked to half-rumours,' says Chandler. And yet it won't, quite, lie down. Mabel Brookes, who included it only as a footnote, could not make herself believe that Napoleon was switched for Robeaud, or that Napoleon survived to be shot in Vienna. And yet she seemed perfectly prepared to accept the truth of Robeaud's disappearance from Baleycourt. 'Probably,' she says, 'it was Roberaud [sic] who became victim of the sentry's gun, in an effort to convey a message to the sick boy.' But as she also quoted the Baleycourt town records - 'Born in this village, died on St Helena' - she did little to clear the fog. Robeaud may have been Napoleon's double, but he cannot have died twice.

Gorbovsky is even more firmly convinced of the Robeaud connection. Having come across Brookes's version, he mentioned it in an article he wrote for an international magazine. Shortly afterwards he received a letter from a reader in France, who had been prompted by his wife. When they first met in 1948, the writer said, she told him that the tomb in Paris contained not Napoleon Bonaparte but the remains of her own great-grandfather. This oft-repeated legend had been told to her, and to anyone else who would listen, by her grandfather, but the story had all but died with him in 1951. The wife's maiden name, no surprise, was Jeanette Robeaud.

Was a different body exhumed?

THE HEAD1821 He is clean-shaven. The disfigured face is unrecognisable.1840 He has hair and a beard. The face is young and noble-looking.

THE BODY1821 The limbs are straight. There is an advanced state of putrefaction.1840 The legs are flexed. The body is embalmed and perfectly preserved.

THE UNIFORM1821 A cockaded hat is on his feet. Silk stockings; boots with silver spurs.1840 The hat has no cockade and is on his thighs. No stockings or spurs.

THE COFFINS1821 Three nested coffins. The outer mahogany coffin is unlined.1840 Four coffins. The outer mahogany coffin is lined with velvet.